This invention relates to photoelectric controls with built-in timers used to energize lamps at a certain level of darkness for a predetermined amount of time.
Lamp adaptors with both a photoelectric control and a timer have been provided by others. Howe et al, U.S. Pat. No. 5,272,418, for example, describes a device that reacts to darkness by energizing a lamp and starting a fixed timer, which will de-energize the lamp when the time expires. typically in six hours. While the timer is counting down the photoelectric devices is disabled to prevent any flickering caused by reflected light.
Others products have been developed that operate similar to Howe's device except that the amount of operating time can be adjusted with some type of mechanical control which is a part of the product. The control is usually a variable resistor.
An object of the present invention is to provide a method of adjusting the operating time of such a product without the use of mechanical devices such as switches or variable resistors.
Another object is to energize and de-energize the lamp instantly, at full power, without disabling the photoelectric control. Light sensing could then continue while the lamp is energized in case the darkness that was reacted to was only temporary, as might occur during a mid-day storm.